upper and lower pic = same bird.
this diffuse GC pattern looks very much like that of a caspian gull. it reminds me of this one:
http://lou.bertalan.de/gulls/m_phi.php?bid=139&grp=cachinnans/mich or http://lou.bertalan.de/gulls/pic/vh/up_0541.jpg
but obviously it is well within micha variation. structure, bill and rest of plumage are good for YLG.